Roles of non-coding RNA in diabetic cardiomyopathy

In recent years, the incidence of diabetes has been increasing rapidly, posing a serious threat to human health. Diabetic cardiomyopathy (DCM) is characterized by cardiomyocyte hypertrophy, myocardial fibrosis, apoptosis, ventricular remodeling, and cardiac dysfunction in individuals with diabetes, ultimately leading to heart failure and mortality. However, the underlying mechanisms contributing to DCM remain incompletely understood. With advancements in molecular biology technology, accumulating evidence has shown that numerous non-coding RNAs (ncRNAs) crucial roles in the development and progression of DCM. This review aims to summarize recent studies on the involvement of three types of ncRNAs (micro RNA, long ncRNA and circular RNA) in the pathophysiology of DCM, with the goal of providing innovative strategies for the prevention and treatment of DCM.


Introduction
Diabetic cardiomyopathy (DCM) is a type of diabetic heart disease with abnormal myocardial structure and function in diabetic patients without other cardiovascular diseases (such as coronary heart disease, hypertension, severe valvular disease, and congenital heart disease) [1,2].Individuals with type 2 diabetes mellitus (T2DM) are estimated to face a 75% higher risk of cardiovascular mortality or hospitalization for heart failure compared with patients without diabetes [3].The underlying mechanisms of DCM, which encompass altered metabolism, mitochondrial dysfunction, oxidative stress, inflammation, cardiac fibrosis, cell death, and extracellular matrix remodeling, have not been fully elucidated and remain subject to debate [4].Disruption in energy substrate utilization [5][6][7], calcium and sodium homeostasis disorder [8][9][10], insulin resistance [11,12], potential involvement of epicardial fat [13][14][15][16], and endothelial dysfunction [17][18][19] are believed to contribute to the onset and progression of DCM.
Non-coding RNAs (ncRNAs) are highly functional and dynamic nucleic acids that do not encode proteins.They include RNAs with specific functions, such as rRNAs, tRNAs, snRNAs, snoRNAs, and microRNAs (miRNAs), as well as RNAs with unknown functions.Long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) are the novel members of non-coding RNA family, but their functions and regulatory mechanisms are still not fully understood.Accumulating evidence indicates that ncRNAs play a crucial role in the regulation of endothelial cells, vascular and smooth muscle cells, cardiac metabolism, ischemia and inflammation.This indicates that ncRNAs hold significant potential in the diagnosis, evaluation, and treatment of DCM.

MicroRNAs
MicroRNAs (miRNAs) are highly conserved, singlestranded ncRNAs typically consisting of 20-22 nucleotides.The typical functionality of miRNAs is to negatively regulate gene expression by binding to target mRNA, leading to either mRNA degradation or inhibition of translation [20].MiRNAs play diverse roles encompassing cardiac hypertrophy, cardiomyocyte apoptosis, autophagy and pyroptosis, myocardial fibrosis, oxidative stress, and other pathophysiological processes, Figs. 1 and 2 [21][22][23][24].The expression pattern of miRNAs during DCM were revealed in 2011.Since then, there have been continuous studies on the role of miRNAs in the development and progression of DCM.

Mitochondrial damage and oxidative stress
Mitochondrial damage and the accumulation of excessive reactive oxygen species (ROS), including reduced oxygen (O 2 ) metabolites, superoxide anion (O 2

LncRNAs
lncRNAs were the heterogeneous RNA transcripts, which are longer than 200 nucleotides, and have many epigenetic regulation forms, including DNA methylation, histone modification and regulation of miRNA [79,80].lncRNAs play essential roles in multiple biological processes, such as chromatin structural changes, transcriptional regulation, post-transcriptional processing, intracellular trafficking, and regulation of enzyme activity [81,82].Recently, growing evidence has suggested that lncRNAs can actively participate in the pathogenesis of diverse cardiovascular diseases, including DCM, Fig. 3.

Cardiac hypertrophy and myocardial fibrosis
Myocardial fibrosis is a critical pathological change observed in DCM.Feng et al. [83] reported increased lncRNA DCRF expression and induced autophagy in cardiomyocytes in high glucose-induced rats.Knockdown of DCRF was found to reduce cardiomyocyte autophagy, attenuate myocardial fibrosis and improve cardiac function in diabetic rats by targeting miR-551b-5p.In another study, Liu et al. [84] indicated that lncRNA NORAD was upregulated in diabetic and DCM mice.Silencing NORAD expression could reduce inflammatory responses, and improve cardiac function and fibrosis in DCM mice via the ceRNA network of NORAD/ miR-125a-3p/Fyn.Moreover, Qi et al. [85] demonstrated that high glucose-induced lncRNA MIAT upregulation was responsible for Interleukin-17 (IL-17) production in cardiomyocytes, which was a pro-inflammatory cytokine and a key regulator of host inflammation.Knockdown of MIAT could significantly attenuate IL-17 expression, ameliorate cardiac fibrosis and improve cardiac contractility.Recent research has also highlighted the involvement of lncRNA Airn in the progression of cardiac fibroblasts in DCM, demonstrating its ability to alleviate diabetic cardiac fibrosis via a m6A-IMP2-p53 axis [86].EndMT was induced by high glucose and drove to cardiac fibrosis.LncRNA DANCR could markedly attenuate high glucose-mediated EndMT in vitro by inhibiting the activation of FoxO1 and increasing the expression of DDAH1 [87].Moreover, Wang et al. revealed that lncRNA TUG1 was upregulated in diabetic mice exposed to high glucose, TUG1 overexpression promoted myocardial fibrosis by suppressing the expression of microRNA-145a-5p [88].These studies underscore the intricate regulatory roles of various lncRNAs in modulating myocardial fibrosis and cardiac function in the context of DCM.

Mitochondrial damage and oxidative stress
Mitochondrial damage and oxidative stress have a significant involvement in the progression of DCM.Recent research has highlighted the upregulation of lncRNA DACH1 in DCM hearts and high glucose-treated cardiomyocytes.DACH1 aggravates DCM by promoting mitochondrial oxidative stress, cell apoptosis, cardiac fibrosis and hypertrophy via increasing ubiquitination-mediated SIRT3 degradation in mice's hearts [89].In a study by Gao et al. [50], it was found that lncRNA HOTAIR expression was significantly decreased in diabetic mice hearts.Knockdown of HOTAIR in high glucoseinduced H9c2 cells resulted in increased oxidative injury.HOTAIR could protect against DCM via activating of the Sirtuin 1(SIRT1) expression by sponging miR-34a [90].Additionally, lncRNA MALAT1 was significantly upregulated in the myocardium of diabetic mice and high glucose-induced cardiomyocytes, mediated oxidative stress, mitochondrial damage and apoptosis through activating the RhoA/ROCK pathway via sponging miR-185-5p.LncRNA H19 is a key lncRNA in DCM, which produces a 2.3-kb non-coding mRNA and is conserved via matriarchal evolution [91].Wang et al. demonstrated that H19 repressed oxidative stress, endoplasmic reticulum stress (ERS) and apoptosis in vitro, furthermore, it reduced cardiomyocytes apoptosis and improved fibrosis in vivo through PI3K/AKT/mTOR signaling pathway [92].

Cell death
Some lncRNAs have been identified to be correlated with cardiomyocyte apoptosis, pyroptosis, ferroptosis and autophagy during the process of DCM.For instance, lncRNAs MALAT1 not only has been implicated in mitochondrial injury, but also participated in cardiomyocyte apoptosis.Zhang et al. [93] reported that Down-regulation of lncRNA MALAT1 could reduce cardiomyocyte apoptosis and improve left ventricular function in diabetic rats.Furthermore, Wang Chong and colleagues [94] Fig. 3 Involvement of lncRNA in the pathogenesis of diabetic cardiomyopathy found that MALAT1 recruited the histone methyltransferase EZH2 to the promoter region of miR-22, thereby inhibing its expression.EZH2, in turn, upregulated the expression of ATP-binding cassette transporter A1 (ABCA1), a known target gene of miR-22.Knockdown of EZH2 was found to enhance cardiac function and prevent cardiomyocyte apoptosis in db/db mice and mouse cardiomyocytes cultured inhigh glucose conditions in the presence of MALAT1.MALAT1 was involved in the processes of cardiac function and cardiomyocyte apoptosis via the EZH2/miR-22/ABCA1 signaling cascade.lncRNA TINCR participated in pyroptosis in DCM progression, which positively regulated NLRP3 by increasing its mRNA stability, downregulating TINCR could suppress pyroptosis and DCM [95].Recently, Xie et al. indicated that lncRNA ZNF593-AS directly interacted with the functional domain of interferon regulatory factor 3 (IRF3), thereby inhibiting the fatty acid-induced phosphorylation and activation of IRF3.This interaction ultimately let to mitigation of cardiac cell death and inflammation in DCM [96].Moreover, lncRNA MIAT was demonstrated to be involve in the progression of cell death in DCM.Xiao et al. [97] reported that MIAT played a vital role in regulating of pyroptosis in DCM via targeting miR-214-3p.Zhou et al. [98] indicated that MIAT knockdown could reduce DAPK2 expression by increasing miR-22-3p, and inhibit apoptosis in cardiomyocytes exposed to high glucose.Ferroptosis is an irondependent regulated necrosis associated with a new form of regulatory cell death [99].Ni et al. [100] showed that inhibition of lncRNA ZFAS1 could alleviate the development of DCM by reducing ferroptosis via stabilizing miR-150-5p to activate CCND2.Interactions of ncRNA are also involved in cardiomyocyte apoptosis.The interaction among NORAD, miRNA-150-5p and ZEB1 has been clarified to influencing the proliferation and apoptosis in HG-induced AC16 cells [101].

Circular RNAs
CircRNAs are produced from precursor mRNAs by the back-splicing of exons in eukaryotes and are widely expressed in a tissue-specific and developmental stagespecific pattern.However, knowledge of these species has remained limited due to their difficult study through traditional methods of RNA analysis [21,102].Cir-cRNAs differ from linear RNAs in that they are circular molecules with covalently closed loop structures, which are involved in a wide range of biological processes, the expression disorder of circRNAs might lead to abnormal cellular functions and disease.CircRNAs may inhibit the translation of mRNAs, altering gene expression by regulating splicing or transcription and by interacting with RNA-binding proteins [103].However, the regulation of circRNAs in cardiovascular diseases remains largely unexplored Fig. 4.
Compared with miRNAs and lncRNAs, the understanding of circRNAs in the molecular mechanisms of DCM is still needs to be improved.Yuan et al. revealed Fig. 4 The role of circRNA in the pathogenesis of diabetic cardiomyopathy that circRNA DICAR was downregulated in diabetic mice hearts and was associated with cardiac dysfunction, cardiac cell hypertrophy, and cardiac fibrosis [104].Yang et al. showed the involvement of another circRNA in the regulation of diabetic myocardial fibrosis.They found that circRNA-0076631 was increased both in high glucose-induced cardiomyocytes and in the serum of diabetic patients, modulated miR-214-3p and its target gene caspase-1 and mediated fibrosis-associated protein resection [105].Zhou et al. reported that circRNA-010567 sponged miR-141 and upregulated target gene TGF-β1, mediated fibrosis-associated protein resection in the diabetic mice myocardial fibrosis model.Silencing the expression of circRNA-010567 could suppress fibrosisassociated protein resection, including Col I, Col III and α-SMA in the regulation of diabetic myocardial fibrosis [106].CircRNA homeodomain interacting protein kinase 3 (circHIPK3) is a particularly abundant circRNA involved in metabolic dysregulation and tumorigenesis [107][108][109].Wang et al. found that circHIPK3 was upregulated in a DCM model of streptozotocin (STZ)-induced diabetic mice [110].CircHIPK3 increased the expression of fibrosis-associated genes, such as COL1A2, COL3A1 and α-SMA, via sponging miR-29b-3p in AngII-induced mouse myocardium [111].Knockdown of circHIPK3 could ameliorate myocardial fibrosis and improve cardiac function in vivo, while decreasing the proliferation of CFs treated with Ang II via miR-29b-3p/Col1a1-Col3a1 in vitro.circRNA circular cerebellar degeneration-related protein 1 antisense (circCDR1as) is degraded by sponging miR-671 via protein Argonaute 2 [112].CircCDR1as was upregulated in DCM hearts of STZ-induced diabetic mice, which promoted cardiomyocyte apoptosis through activating the MST1-Hippo pathway in vivo and in HG-treated primary cardiomyocytes.Knocking down CDR1as inhibited cardiomyocyte apoptosis in DCM [113].Recently, a novel circRNA mitogen-activated protein kinase kinase kinase 5 (circMAP3K5) was found to regulate apoptosis of cardiomyocytes in DCM.Shen et al. indicated that circMAP3K5 upregulated in in high glucose-induced H9c2 cardiomyocytes, accelerated cardiomyocytes apoptosis through the miR-22-3p/ death-associated protein kinase 2 (DAPK2) axis [114].Fu et al. found that circ-0071269 was significantly overexpressed in H9c2 cells upon treatment with high glucose.Circ_0071269 could promote the development of DCM through the miR-145/GSDMA axis.Knockdown of circ_0071269 promoted cell viability and inhibited the inflammatory response, cytotoxicity, and pyroptosis of H9c2 cells in vitro [115].

Clinical application
NcRNAs are involved in the development and progression of DCM, presenting in the blood are extremely stable and can be potentially used as diagnostic and prognostic biomarkers for cardiovascular diseases, consequently allowing early intervention.Furthermore, ncRNAs are modulating various biological pathways, suggesting that these molecules may be harnessed as a novel therapeutic strategy in treating DCM.
Vildagliptin is an oral hypoglycemic drug that reduces hyperglycemia in T2DM.Li et al. reported that vildagliptin could enhance cardiac function in type 2 diabetic mice by restoring autophagy and alleviated fibrosis through the miR-21/SPRY1/ERK/mTOR pathway [66].Melatonin is a hormone produced by the pineal gland, and it has extensive beneficial effects on various tissues and organs.Che et al. showed that melatonin administration significantly ameliorated cardiac dysfunction and reduced collagen production via inhibiting lncRNA MALAT1/miR-141-mediated NLRP3 inflammasome and TGF-β1/Smads signaling pathway, while the expression of TGF-β1, p-Smad2, p-Smad3, NLRP3, ASC, cleaved caspase-1, mature IL-1β, and IL-18 were downregulated in the heart of mice with diabetes mellitus following melatonin treatment [116].Furthermore, melatonin was reported to alleviate cardiac dysfunction and cardiomyocyte apoptosis in diabetic rats, notably by downregulating lncRNA H19/MAPK and upregulating miR-29c levels [117].Diallyl trisulfide (DATS) is an anti-oxidant in garlic oil, can inhibit stress-induced cardiac apoptosis and can be used as a cardioprotective agent.Lin et al. found that the DATS could mediate AGE-induced cardiac cell apoptosis attenuation by promoting FoxO3a nuclear transactivation to enhance miR-210 expression and regulate JNK activation [77].Pomegranate peel extract (PPE) exhibits a cardioprotective effect due to its anti-oxidant and antiinflammatory properties, which could significantly ameliorate cardiac hypertrophy in diabetic rats and increase the survival rate.The protective effect of PPE on DCM could be due to the inhibition of the NLRP3/caspase-1/ IL-1β signaling pathway and downregulation of lncRNA-MALAT1 [118].Berberine (BBR) is a natural compound extracted from a Chinese herb (Rhizoma coptidis; known as 'Huang Lian' in Chinese).It has been traditionally used in Chinese medicine for treating inflammatory disorders and cardiovascular injury induced by diabetes mellitus [119].Yang et al. indicated that BBR alleviated DCM by inhibiting miR-18a-3p-mediated gasdermin D (Gsdmd) activation [120].Citronellal (CT), a monoterpenoid natural product extracted from the grass plant Citronella, has demonstrated anti-thrombotic, antihypertensive and anti-diabetic cardiomyopathy properties.Qiu [122].Ranolazine increased miR-135b expression in cardiac fibroblasts exposed to high glucose.Furthermore, miR-135b directly interacted with caspase-1.Thereby, ranolazine could reduce pyroptosis, inhibit collagen deposition and improve cardiac function in rats by upregulating miR-135b [42].Activation of cardiac miR-132 leads to adverse remodeling and pathological hypertrophy.CDR132L, a synthetic antisense oligonucleotide that selectively blocks pathologically elevated miR-132, has shown promisingeffects on heart failure (HF) in the early stage following myocardial infarction (MI) in phase I/II trials [123][124][125].There are many opportunities for further advancement in cardiovascular medicine, particularly in the new therapeutics to target ncRNAs for diabetic DCM, through conducting large-animal studies and phase I/II trials involving humans.

Conclusions
In the present review, we provide an overview of the recent advancements in understanding the role of ncRNAs in the pathogenesis of DCM.Various ncRNAs play crucial roles in regulating cardiomyocyte hypertrophy, myocardial fibrosis, apoptosis and autophagy, oxidative stress and inflammatory response, all of which are key mechanisms associated with DCM, Table 1.With the growing epidemic of diabetes mellitus and its related cardiac complications, the potential of ncRNA as promising attractive biomarkers and therapeutic targets for DCM and heart failure has captured significant attention within the scientific community.The identification and characterizations of ncRNAs and the pathways they influence may pave the way for the development of innovative treatments to manage or combat diabetic cardiomyopathy in the near future.

Table 1
Regulation information of ncRNAs in diabetic cardiomyopathy